Piston



W. C. M COY June 12, 1934.

PISTON 2 Sheets-Sheet 1 Filed Oct. 12, 1928 u: m WM QN m m E m W June12, 1934. v w. c. MccoY 1,963,026

PISTON Filed Oct. 12 1928 2 Shets-Sheet 2 l/ 6 him I 4 ATI'ORNEYSPatented June 12, 1934 UNITED STATES PATENT OFFICE PISTON William C.McCoy, Cleveland Heights,

'signor to The Cleveland Trust Company, Cleveland, Ohio, a corporationof Ohio Application October 12, 1928, Serial No. 312,067

8 Claims.

This invention relates to pistons and more particularly to pistons forinternal combustion engines made of a relatively light metal such asaluminum and its alloys, which havea relatively high coefiicient ofexpansion as compared to the metal of the cylinder in which the pistonis used.

The present invention has for its object to provide a piston which,during the explosion stroke has one side in full engagement with thecylinder wall, in order to obtain the advantages of better lubrication,greater area of contact and more it the relative lateral movement of thepiston body and the piston ring at the position of the thermallyresponsive element to thereby center the piston with respect to the ringduring the compression stroke and to permit full engagement of theopposite side of the piston with the cylinder wall during thecompression stroke.

A further object is to provide a thermally responsive element in theform of a strut within the piston which provides normal operation of thepiston ring on the explosion side of the piston head and provides arigid backing for the piston ring on the side of the piston againstwhich pressure is brought on the compression stroke, the strut having acoefficient of expansion such as to automatically prevent objectionalshifting of the piston head with respect to the cylinder during thecompression stroke.

With the above and other objects in view, the invention may be said tocomprise the piston as illustrated in' the accompanying drawings hereinafter described and particularly set forth in the appended claims,together with such variations and modifications thereof as parent to oneskilled in the art to vention appertains.

Reference should be had to the accompanying drawings forming a part ofthis specification in which:

I Figure 1 is a side elevation of a piston embodying the invention.

will be apwhich the in- Fig. 2 is an axial section through the pistonshown in Fig. 1.

Ohio, as-

Fig. 3 is a top plan view of the piston shown in Fig.1.

Fig. 4 is a top plan view of the strut detached from the piston.

Fig. 5 is an axial section through a piston embodying the invention inaslightly modified form.

Fig. 6 is a view similar to Fig. 5 showing the strut in the form inwhich it is cast into the cylinder body.

Fig. 7 is an Fig. 8 is a right angles to that shown axial. section takenin a plane at in Fig. 6.

plan view of the strut detached from the cylinder.

Fig. 9 is a side elevation of the strut.

Fig. 10 is a plan view of the core employed for spacing the body of thestrut from the piston head in the casting operation. I

Fig. 11 is an end elevation of the core.

As shown in the accompanying drawings, the piston is in the form of acasting having a. head 1, and a cylindrical skirt 2, integral with thehead and which has integral Wrist pin receiving bosses 3. The head witha pluralit rings 5.

At the bottom of one of portion of the y of circumferential grooves 4maexpansible bearing the grooves 4, there is a circumferentiallyelongated slot 6 extending through the wall of the piston body and thisslot is adapted to receive which is preferably strip. The strut 7 theinterior of the outer end of a strut 7 in the form of a flat metalextends diametrically across the piston immediately beneath the head 1and at right angles to the axis of the wrist pin. The outer end of thestrut 7 is positioned in the bottom slot opens and of the ring grooveinto which the the opposite end of the strut bears against the wall ofthe piston at a diametrically opposite point. In order to rigidly securethe strut 7 in place, the wall of the piston may be provided with agroove 8 to receive the end of the strut and the head of the piston maybe provided with an inwardly projecting lug 9 which may be engaged by atongue 10 struck up from the body of the strut,

The strut 7 may be inserted into the piston through the slot 6 until itsinner end engages in the groove 8, after which the tongue 10 is forcedoutwardly into engagement with the lug 9 to securely lock the strut inplace. The outer end edge of the strut 7 may be ground to the correctdiameter after the strut has been secured in place, as above described.

The strut may be formed of steel or other metal which has a c oeificientof expansion lower than piston is provided the coemcient of expansion ofthe metal of the piston, the coefiicient of expansion of the strut beingsuch that when the ring engages with the wall of the'cylinder and withthe end of the strut, the head of the piston body will be in relativelyclose bearing contact with the explosion thrust sideof the cylinder,regardlesss and the cylinder.

1 contact with the cylinder wall. During the compression stroke, thethrust on the piston is toof the amount of play between the piston bodyThe piston ring is a resiliently expansible ring which maintainscircumferential ward the side of the piston at which the strut 7 thecylinder wall presses the ring 5 against the pression stroke.

I It will be apparent that with the cylinder, the piston and the bearingring formed of metals havink known coefiicients of expansion, thecoefilcient of expansion of the strut which maintains the; piston bodyin proper working relation with respect to the cylinder during thepressure stroke at any working temperature may be computed, thecoefficient of expansion of the strut being a function of thecoefficients of expansion of the cylinder, piston and bearing ring. Thestrut will be made of metal having approximately the theoreticalcoeflicient of expansion, the coefficient of expansion of the strutbeing ordinarily less than that of the piston and of the cylinderbecause of the higher working temperature of the piston head as comparedwith the cylinder wall.

During the compressionstroke, the pressure against the cylinder-wall isnot excessive and can be advantageously taken up by the piston rings. Onthe explosion stroke,- however, the lateral pressure against thecylinder, wall is very much greater and if this pressure is, takensolely upon pressure per unit of area is a piston ring, the

The present excessive and the wear is excessive.

invention, however, avoids this difliculty by providing a rigid backingfor the piston ring only on the side of the piston against whichpressure is exerted during the compression-stroke. On the other hand,the piston .body has full engagement with the wall of the cylinderduring the explosion stroke.

Figs. 5 to 11 of the drawings show a modified forin of the invention inwhich the strut is permanently anchored in the body of the piston. Inthis modification, the strut 11 is provided at its inner end with alaterally bent fork portion 12, which is embedded in the body of thepiston by casting the piston with the end 12 projecting into the moldcavity.

' As shown in Fig. 5, 11 projects through a slot 13 in the wall of thecylinder that extends therethrough and into the bottom of acircumferential ring groove 14, the end of the strut being sufiicientlyfree to move in the slot 13 to compensate for expansion of the pistonbody and the strut having a coefficient of expansion corresponding tothat of the strut in the modification first described. The action of thestrut in substantially holding the piston body against one wall of thecylinder and thereby limiting the lateral movement thereof is the sameas that of the strut? first described. In casting the piston, it isdesirable that the strut lie entirely within the piston and for this theouter end of the strut reason, the central portion of the strut is bowedas shown at 15 in Fig. 6 so that the outer end of the strut is supportedwithin the cylindrical cavity of the mold in which the wall of thepiston is formed.

The head of the piston is provided with an inwardly projecting rib 16which bears against the outer face of the strut 11 to provide a rigidbacking for the strut and opposite the body portion 15 of the strut, therib 16 is provided with a concavity 1'I. After thepiston is cast, theexterior thereof is turned to the desired diameter and the ring grooves14 are cut therein. The slot 13 is then cut through the wall from thebottom of the groove opposite the end of the strut 11. The body portion15 of the strut is then straightened by pressing the bowed portion 15against the rib 16 and into'the recesses 17 to reverse the stresses inthe metal so that itwill spring back 'to substantially straightposition, causing the outer end of the strut to be forced outwardlythrough the slot 13into the bottom of the groove 14. In order toseparate the body of the strut 11 from the head of the casting duringthe casting operation, and to form concavity 1'! in the rib 16, a coresuch as shown at 18 in Figs. 10 and 11 is placed in the mold. beneaththe body portion 15 of the strut.

It will be apparent that the present invention provides a very simpleand effective device for limiting the play of the piston in the cylinderwithout sacrificing the advantage of full contact of the piston with thecylinder during the explosion stroke.

It will also be apparent that the device of the present invention addsbut little to the cost of manufacture of the piston.

particular form of apparatus shown and described, andthe particularprocedure set forth,

are presented for purposes of explanation and illustration and thatvarious modifications of said apparatus and procedure can be madewithout departing from my invention as defined in the appended claims.

What I claim is:

1. A piston for internal combustion engines having an external ringgroove, an expansible bearing ring in said groove, and a thermally re--sponsive element engaging the interior of said ring at a single point inits circumference to limit the movement of the ring into the groove atsaid point.

2. A piston for internal combustion engines having an external ringgroove, an expansible bearing ring in said groove, and a thermallyresponsive element engaging the interior of said ring at a single pointin its circumference to limit the movement of the ring into the grooveat said point, said point of engagement being diametrically opposite theface of the piston which bears against the/cylinder wall on theexplosion stroke.

3. A hollow piston having a head provided with an external ring groove,a circumferentially elongated slot in the bottom of said grooveextending through the wall of the piston, a strut in the form of a flatmetal strip extending diametrically across the piston and having one endslidably fitting in said slot and its opposite end bearing against theinterior of the piston wall, at a'point diametrically opposite the slot.

4. A piston for internal combustion engines having an external ringgroove, an expansible bearing ring mounted in said groove, and athermally responsive element having one end in engagement with theinterior of said ring at a single point in its circumference directlyopposite the explosion thrust side of said piston to limit the movementof said bearing ring into the groove at said point, the other end ofsaid thermally responsive element being rigidly secured to the wall ofsaid piston at said explosion thrust side.

5. A piston for internal combustion engines having a head provided witha ring groove, a circumferentially elongated slot in the bottom of saidgroove extending through the piston wall, a flat thermally responsivestrut extending diametrically across said head and having one endslidably fitting in said slot and its opposite end rigidly secured tothe interior of the piston wall at a point diametrically oppositeisaidslot, and an expansible bearing ring mounted in said groove, said firstmentioned end of said strut engaging the interior of said ring at asingle point in its circumference to limit the movement of the ring intothe groove at said point.

6. A piston for internal combustion engines having a head provided witha ring groove, a circumferentially elongated slot in the bottom of saidgroove extending through the side wall of said head at a pointdiametrically opposite the explosion thrust side of said piston, a fiatthermally responsive-strut extending diametrically across said head andhaving one end slidably fitting in said slot and its opposite endrigidly secured to the piston body at the explosion thrust side thereof,and an expansible bearing ring mounted in said groove, said slidable endof said strut engaging the interior of said ring at a single point inits circumference to limit the movement of said ring into said groovediametrically opposite the explosion thrust side of said piston.

7. A hollow piston having 'an external ringgroove and an opening throughthe wall of the piston to the bottom of said groove, a bearing ring insaid groove, and a strut within the piston affixed at one end to thebody of the piston and out of engagement with said ring and having itsopposite end extending through said opening into said groove to engagethe interior face of said ring at one end only of said strut.

8. A piston having an external piston ringgroove and an opening throughthe wall of the piston to the bottom of said groove, a piston ring insaid groove, and a strut within the piston having one end extendedthrough said opening and engaged with the interior face of said ring andhaving its WILLIAM c. MCCOY.

